Re: Is this enough for us to have triple-parity RAID?

[Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>]

Hi Peter,

> > Yes, being a generator for GF(2^8) is a requirement for a parity
> > generator (sorry for the confusing terminology here - if anyone has a
> > better suggestion, please say) to be part of a 255 data disk system.
> > However, being a GF generator is necessary but not sufficient - using
> > parity generators (1, 2, 4, 16) will /not/ give quad parity for 255 data
> > disks, even though individually each of 1, 2, 4 and 16 are generators
> > for GF.
[...]
> It is also worth noting that there is nothing magical about GF(2^8).  It
> is just a reasonable tradeoff when tables are needed.

I, then, ask you too.

What is this story that being a generator is not enough?

Is there any reference, documentation, link which can be
studied in order to understand this limitation?

In all RS papers I found, the only constrain put was that
the Vandermonde must be constructed with generators.
Not all RAID examples used them, but no paper, at least
for what I understood, was limiting the generators to
be also "independent".

Any undestandable explanation?

Thanks,

bye,

-- 

piergiorgio